Suction hood



Feb. 28, 1950 M. l. DORFAN 2,499,3m

SUCTION HOOD Filed Sept. 23, 1948 2 Sheets-Sheet l Mum 1w. .4 TTORY M. l. DORFAN Feb. 28, 1950 SUCTION HOOD" Filed Sept. 25, 1948- 2 Sheets-Sheet 2 Fig. 2

INVENTOR.

fizOQTON DORFAN B A TTR IVES Patented Feb. 28, 1950 UNITED STATES PATENT omcs American Wheel-abrator oz Equipment Corporation; Mishawaka, lnclL, a corporation of Delaware Application September 23, 1948, serial'No. 50,767

(or. sozss) 6 Claims.

This invention relates to improvements in pneumatic conveying and dust collecting systems and prov-ides an improved suction hood particularlysuited for use as a grading hood incor oratin'g numerous features and advantages which will become apparent from the following" description.

Finely divided material such as fibrous 'Or granular materials, for example asbestos fibers, are commonly separated from impurities and graded according to particle or finer s'ize'by a pneumatic grading apparatus in which the material is moved underneath ="or past a suction hood "forming part of a pneumatic conveying system.

A stream of air passing over or through the mate ial and flowing into the grading hood selectively acts on the particles or fibers in pickingup and carrying with it particles or fibers up to a certain size, depending on the intensity of the air 'fiow, while leaving "larger orheavier "particles behind. A similar procedure maybe used for the grading of materials which occur in other finely divided states, "for example for granular or powdered materials. In every instance themater'ial to be graded is 'subj ectedto the influence of a stream of airor' other pressure fluid whichca'rries particles up to a predetermined size with it, whilerejecti-ngparticles ofiar'ger size.

Suction hoods used io'r grading or other purposes are "commonly adjusted "for predetermined air volumes or air ve'loeitiesat the mouth of the hood by raising or lowering'the hood'with respect to the surface supporting the" material to be graded, for example a vibrating table over which the fibers to be graded'are fed.

Another conventional manner -o'f 'ad'ju'stnieht involves throttling of the air now enterin'g'the hood by means of a damper in the airpassa'ge extendingfror'n the hood.

Bother manners of adjustment are wasteful.

'When the hood is raised a large percentage of The 'l'o'sses thus caus'ed are consideralili'e and appear in terms'er additional :hor eipcw required for driving -the fans which-produce-mean- ;floW.

The present -iinventionprovides-a suetionnobd aforementioned losses and which, in addition, provides the feature of adjustability for any desired fractional volume of its total capacity. The improved hood is so constructed that even under conditions of reduced now, an efficient form of passage is maintained so that losses due to turbulen'ce are eliminated. Sudden changes in direction of the new at the mouth of the hood are also avoided'b'y providing the hood with 'a suitably shap'ed'lip section.

The various structural and operational features and advantages of this invention as well as its objects will appear more fully from the detailed description which follows accompanied by drawings showing, for the purpose of illustration, a preferred embodiment of the invention. The invention also consists in certain new and original features 'of-=construction and combination of elements hereinaiterzset forth and claimed.

Although-the characteristic features of this invention which are believed to be novel will be particularly pointed 'out in the 'calims appended hereto, the invention itself, its objects and advantages, and the manner in which it may be carried out ina'y'bebetter understood by referring to the following description taken in connection with the accompanying drawings forming a part of it in which:

Figure 1 is a front elevational view of a suction h'o'o'd'leading to two conveyor ducts, and

Figure 2 is a side elevational view, partly in section, of the hood shown in Figure .1, a section being taken on line-22 of Figure 1.

' tended to be as generic in their application as "of im roved construetion wnicnzis tree ztrcin the 55 stood-that the details"may be modified in various respects without departure from the principles of the invention and that the invention-maybe applied-to other structures than the one shown.

"The suction hood shown in Figure 1 is particu- :lar1y'ne'signed as a-gr'adinghood serving a plu- 'rality" of conveyor ducts, such as two ducts ll and 12. 'frhe?hood comprises enclosing Wallsiifneluding fixed end walls as and I4 whoselower edges and 1e are spaced at predetermined distancefl -abcve acmatenal supporting surface I! or may extend below it. The surface 11 may be a vibrating deck or screen panel of conventional construction and is preferably inclined with respect to the horizontal H at any angle, so that divided material slowly advances over the table surface under the action of gravity when the table is shaken or vibrated, thus passing underneath the hood in the direction indicated by arrow I8.

The enclosing walls of the hood further include side walls [9 and 20. These side walls comprise several articulated sections or portions adapted to be adjusted with respect to one another for the purpose of varying the shape of the passage formed by them. I

The side wall [9 comprises a fixed inner side wall portion 2| to which an adjustable intermediate side wall portion 22 is hingedly connected along a hinge axis 23. A piano hinge 24 is preferably used for this purpose for reasons of airtightness.

Similarly, a lip portion 25 is hingedly connected to the intermediate portion 22 along a. hinge axis 26, also preferably formed by a piano hinge 21. shape, may be plane or curved, but is preferably made of semi-cylindrical curvature to provide a gradual outwardly curving mouth for the hood.

The length of the adjustable intermediate wall portion 22 and of the lip portion 25 is such that these wall portions fit reasonably snugly with their side edges between the end walls 14 and I so that no undue air leaks exist along the side edges.

The opposite side wall comprises a fixed inner side wall portion 28 to which an intermediate side wall portion 29 is hinged along a hinge axis 38, preferably formed by a piano hinge 3|. A lip portion 32 is hingedly connected to the intermediate side wall portion 29 along a hinge axis A 33, also preferably formed by a piano hinge 34.

The lip portions and 32 are so mounted that their lowermost portions remain substantially in a plane parallel to the material supporting surface or deck I! when the intermediate side wall,

portions 22 and 29 are swung towards or away from each other about their hinge axes 23 and 30, respectively. In a construction employing curved lip portions 25 and 32, as shown in the drawings, this is conveniently accomplished by supporting the far edges 35 and 36 of the lip portions for movement along a predetermined path, for example for swinging movement about pivotal axes 3'! and 3B. The radius, that is the distance between the pivotal axes and the respective edge 35 and 36 as represented by radius rods 43 and 44 is so selected with respect to the distance between the axes 23, 21 and 30, 33, respectively, that the lowermost portions of the lip sections 25 and 32 remain in substantially a plane parallel to that of the deck or surface II. This plane, in the illustrated embodiment, is the plane tangential to the curved lip portion 25 or 32. The distance d between the mouth of the hood and the deck or surface I! remains unchanged for the various positions of adjustment of the side wall portions of the hood.

As Figure 2 clearly shows, the adjustable walls of the hood provide an entrance passage of Venturi shape and Venturi flow characteristics.

entrance or mouth portion 39 narrows gradually towards a throat portion 40, and thence gradually widens at M towards a further portion of the duct 42 which is substantially rectangular and of constant cross-section andgradually changes The lip portion may be of any desired into the circular cross sections of the ducts H and I2.

Suitable mechanism is provided for arresting the wall portions of the hood in any predetermined position of adjustment. In the illustrated form of apparatus, this mechanism comprises curved bars 45 and 46 secured to the intermediate side wall portions 22 and 29 at 41 and 48, respectively. The adjustment bars may be frictionally clamped to brackets 49 and 50 by bolts 5| and 52.

Several positions of adjustment of the side walls I9 and 20 are indicated in broken lines in Figure 2. It is apparent that in all positions of adjustment abrupt changes in the direction of flow of air entering the suction hood are prevented and that the hood retains the characteristic form of a Venturi passage, whereby losses due to formation of a vena constricta are prevented. Throughout the range of adjustment freedom from turbulence is maintained and, correspondingly, efficient operation is insured.

Adjustable vanes 53 and 54 may be mounted inside the hoods for the purpose of distributing the entering air evenly over the cross section of the hood and of the attached conveyor ducts l2 and i 3. These vanes are pivotally mounted at 55 and 56 and may be moved to and arrested in, any desired angular position by wing nuts 5'! and 58 on bolts 59 and 60. The bolts 59 and 60 extend through arcuate slots GI and 62 in quadrants 63 and 64 against which the wing nuts are tightened.

The invention thus provides an improved suction hood offering many features and advantages. The hood is simple of construction, relatively inexpensive to manufacture and is simple to main tain, adjust and operate.

Its flow characteristics are particularly favorable in that changes in the flow passing through the hood do not affect or reduce the efiiciency of the hood as distinguished, for example, from damper control hoods where turbulence of air is set up at the point of greatest restriction leading to power losses.

In addition, greatest efficiency is maintained by avoidin raising and lowering of the hood with respect to the material supporting table or surface and by installing the hood at an optimum distance d which is so selected that the entire volume of air entering the hood passes through, or agitates, the material particles to be graded. Thus the entry of idle air as, for example in the case of a raised hood, is prevented and a correspending amount of power is saved.

Installation of the improved suction hood in existing installations leads to a considerable increase in efliiciency.

In a typical installation employing damper controlled grading hoods, one hundred eighty tons of air per hour were required to pick up and convey ten tons of asbestos fibers per hour. Installation of the improved suction hoods embodying the invention reduced the air requirement by approxi- .mately one-third, to less than one hundred twenty tons, resulting in a corresponding saving in power. Since power is a continuous expense in installations of the aforementioned kind, a saving of power of the order of twenty-five per cent through installation of improved suction hoods results in a very substantial saving.

Simplicity of construction and ease of adjust- ,ment are further features distinguishing the invention over conventional structures.

Obviously, the present invention is not restricted to the particular embodiment or form of construction herein shown and described. Therefore, numerous modifications, additions, omissions, substitutions and other changes may be made without departing from the spirit and the essence of the invention.

What is claimed is:

1. A suction intake for pneumatic conveying ducts, comprising a material supporting surface; and a suction hood spaced from said surface, the hood including enclosing side walls so disposed with respect to one another as to providea Venturi shaped intake passage normally having an outer portion adjacent said surface converg' 2. A suction hood for pneumatic conveying ducts, said hood havingenclosing side walls at least one of the side walls comprising an inner portion, an intermediate portion hingedly connected to said inner portion and a lip portion hingedly connected to said intermediate portion,

said intermediate and lip portions being so adjustable with respect to each other and to said inner wall portion to form a Venturi shaped passage normally converging towards a throat and diverging on the other side of said throat, whereby the flow through said passage may becontrolled by adjustment of the width of the throat.

3. A suction hood for pneumatic conveying ducts, said hood comprising enclosing walls including end walls and side walls, at least one of H the side walls being articulated to comprise a fixed inner side wall portion, an intermediate side wall portion hinged to the inner side wall portion and a lip portion hinged to the intermediate portion, said articulated side wall being adjustable with respect to the side wall opposite it to form a Venturi-shaped passage with the re-- maining walls having a throat portion of variable width at the hinged joint between said intermediate portion and the lip portion.

4. A suction hood for pneumatic conveying ducts, said hood comprising enclosing walls including a pair of opposed fixed end walls and a pair of opposed articulated side walls, each side wall comprising a fixed inner side wall portion, an intermediate side wall portion hinged to the inner side wall portion and an outwardly curved lip portion hinged to the intermediate portion, said articulated side walls being adjustable to form with the end walls a Venturi-shaped passage having a throat portion of variable width at the hinged joint between said intermediate portion and the lip portion.

5. A suction hood for pneumatic conveying ducts, said hood comprising enclosing walls including a pair of opposed fixed end walls and a pair of opposed articulated side walls, each side wall comprising a fixed inner side wall portion, an intermediate side wall portion hinged to the inner side wall portion, and an outwardly curved lip portion hinged with one end to the intermediate portion; means for hingedly supporting the other end of said lip portion at a radius so selected with respect to the length of said intermediate portion that the plane tangential with respect to said curved lip portions remains substantially unchanged when said intermediate wall portions are moved towards, or away from each other; and means for arresting said intermediate wall portions in adjusted position, whereby a Venturi-shaped passage is formed having'a throat of variable width controlling the flow through said passage.

6. A suction hood for pneumatic conveying ducts, said hood comprising two substantially parallel end walls; a pair of inner side walls extending between said end walls; a pair of intermediate side walls hingedly connected to said inner side walls and movable towards and away from each other between said end walls; a pair of semi-cylindrically curved lip portions hingedly connected with one side edge to said intermediate side walls and extending substantially from one end wall to the other; means for supporting each lip portion for movement of its opposite side edge along a path such that the plane tangential with respect to said curved lip portions remains substantially unchanged when said lip portions are moved towards or away from each other; and means for arresting said li portions in adjusted positions, whereby the width of the passage defined by said end walls and lip portions may be varied.

MORTON I. DORFAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 782,260 Milne Feb. 14, 1905 2,367,507 Kittler Jan. 16, 1945 

